1. Field of the Invention
The present invention relates to computer systems, and more specifically, to providing an audio signal to headphones, internal loudspeakers or external loudspeakers using a combination jack.
2. Description of the Related Art
Multimedia capabilities are an important feature in today's computer system. As processor capabilities are improving in each generation of new computer systems, so are the needs for providing sights and sounds to the user.
Today's computer systems from the personal computer to workstations run the gamut of software applications. Software applications such as games, word processing, finance, computer aided design (CAD) and communications may be installed on one computer. Thus, users demand hi-resolution graphics display and/or high quality sound reproduction capabilities for these applications.
To meet the demands, computer manufacturers are building larger monitors, better video controllers, and improved sound devices. The sound devices provide electrical signals to headphones or loudspeakers for sound reproduction. Furthermore, the computer system may allow users to listen to sounds either with headphones, internal loudspeakers, or external loudspeakers.
Typically, sounds are reproduced by the internal loudspeaker. However, for personal listening, a user may plug the headphones into the computer system headphone jack. Typically, computer systems have switching circuitry which disables the internal loudspeakers when a headphone plug is inserted into the headphone jack. Thus, the user may enjoy the sounds and not disturb others via the internal loudspeakers.
Furthermore, if the user plugs the external loudspeakers into the line-out jack of the computer system, the computer system's switching circuitry disables the internal loudspeakers. External loudspeakers typically provide better audio performance than internal speakers. Therefore, to prevent interference with the external loudspeakers, the switching circuitry disables the internal loudspeakers.
Typical computer systems use many different jacks for accepting a wide range of input/output (I/O) devices, such as a headphone, external loudspeaker, a joystick, and a MIDI device, such as a musical keyboard. Some prior jacks have included switching circuitry. The switch would be in a particular position based on whether a plug is inserted or not inserted into the jack. These jacks allow engineers to design circuits for routing audio signals to an output, based on whether a plug is inserted into a particular jack. The jacks typically provide enabling signals based on whether a plug is inserted. Recently, a combination jack, incorporating the different jacks in a single package for the different I/O's, has begun to be used in an attempt to provide a low cost standard for the industry.
However, the combination jack does not provide the audio enabling/disabling capabilities. Therefore, computer design is faced with two conflicting concerns. A jack with switching capability, but not compatible with the combination jack could be used to allow the routing of audio signals to a headphone internal loudspeakers or external loudspeakers under varying use conditions. However, this type of jack is not in conformance with the desired features of the combination jack.